保险有效的实现两星期内自动登陆功能

自动登陆流程：
1．? 保存用户信息阶段：
当用户登陆网站时，在登陆页面填写完用户名和密码后，如果用户在提交时还选择了“两星期内自动登陆”复选框，那么在后台程序中验证用户名和密码全都正确后，还要为用户保存这些信息，以便用户下一次可以直接进入网站；如果用户没有勾选“两星期内自动登陆”复选框，则不必为用户保存信息，那么用户在下一次登陆网站时仍需要填写用户名和密码。
在保存用户信息阶段，主要的工作是对用户的信息进行加密并保存到客户端。加密用户的信息是较为繁琐的，大致上可分为以下几个步聚：
① 得到用户名、经MD5加密后的用户密码、cookie有效时间(本文设置的是两星期，可根据自己需要修改)
② 自定义的一个webKey，这个Key是我们为自己的网站定义的一个字符串常量，这个可根据自己需要随意设置
③ 将上两步得到的四个值得新连接成一个新的字符串，再进行MD5加密，这样就得到了一个MD5明文字符串
④ 将用户名、cookie有效时间、MD5明文字符串使用“：”间隔连接起来，再对这个连接后的新字符串进行Base64编码
⑤ 设置一个cookieName,将cookieName和上一步产生的Base64编码写入到客户端。
2．? 读取用户信息：
其实弄明白了保存原理，读取及校验原理就很容易做了。读取和检验可以分为下面几个步骤：
① 根据设置的cookieName，得到cookieValue，如果值为空，就不帮用户进行自动登陆；否则执行读取方法
② 将cookieValue进行Base64解码，将取得的字符串以split(“:”)进行拆分，得到一个String数组cookieValues（此操作与保存阶段的第4步正好相反），这一步将得到三个值：
?????? cookieValues[0] ---- 用户名
?????? cookieValues[1] ---- cookie有效时间
?????? cookieValues[2] ---- MD5明文字符串
③ 判断cookieValues的长度是否为3，如果不为3则进行错误处理。
④ 如果长度等于3，取出第二个,即cookieValues[1]，此时将会得到有效时间（long型），将有效时间与服务器系统当前时间比较，如果小于当前时间，则说明cookie过期，进行错误处理。
⑤ 如果cookie没有过期，就取cookieValues[0]，这样就可以得到用户名了，然后去数据库按用户名查找用户。
⑥ 如果上一步返回为空，进行错误处理。如果不为空，那么将会得到一个已经封装好用户信息的User实例对象user
⑦ 取出实例对象user的用户名、密码、cookie有效时间（即cookieValues[1]）、webKey，然后将四个值连接起来，然后进行MD5加密，这样做也会得到一个MD5明文字符串（此操作与保存阶段的第3步类似）
⑧ 将上一步得到MD5明文与cookieValues[2]进行equals比较，如果是false，进行错误处理；如果是true，则将user对象添加到session中，帮助用户完成自动登陆

?

CookieUtil.java
处理cookie的工具类,包括读取,保存,清除三个主要方法。
package cn.itcast.util;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import cn.itcast.bean.User;
import cn.itcast.dao.UserDAO;
import cn.itcast.factory.DaoImplFactory;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
/*
?* 2007.09.21 by lyhapple
?* */
public class CookieUtil {
?????? //保存cookie时的cookieName
?????? private final static String cookieDomainName = “cn.itcast”;
?????? //加密cookie时的网站自定码
?????? private final static String webKey = “itcast”;
?????? //设置cookie有效期是两个星期，根据需要自定义
?????? private final static long cookieMaxAge = 60 * 60 * 24 * 7 * 2;
?????? //保存Cookie到客户端--------------------------------------------------------------------
?????? //在CheckLogonServlet.java中被调用
?????? //传递进来的user对象中封装了在登陆时填写的用户名与密码
?????? public static void saveCookie(User user, HttpServletResponse response) {
????????????? //cookie的有效期
????????????? long validTime = System.currentTimeMillis() + (cookieMaxAge * 1000);
????????????? //MD5加密用户详细信息
????????????? String cookieValueWithMd5 =getMD5(user.getUserName() + ":" + user.getPassword()? + ":" + validTime + ":" + webKey);
????????????? //将要被保存的完整的Cookie值
????????????? String cookieValue = user.getUserName() + ":" + validTime + ":" + cookieValueWithMd5;
????????????? //再一次对Cookie的值进行BASE64编码
????????????? String cookieValueBase64 = new String(Base64.encode(cookieValue.getBytes()));
????????????? //开始保存Cookie
????????????? Cookie cookie = new Cookie(cookieDomainName, cookieValueBase64);
????????????? //存两年(这个值应该大于或等于validTime)
??? ???????? cookie.setMaxAge(60 * 60 * 24 * 365 * 2);
??? ???????? //cookie有效路径是网站根目录
???????????? cookie.setPath("/");
????????????? //向客户端写入
????????????? response.addCookie(cookie);
?????? }
?????? //读取Cookie,自动完成登陆操作--------------------------------------------------------
?????? //在Filter程序中调用该方法,见AutoLogonFilter.java
?????? public static void readCookieAndLogon(HttpServletRequest request, HttpServletResponse response,
??? ??? ??? FilterChain chain) throws IOException, ServletException,UnsupportedEncodingException{
??? ??? //根据cookieName取cookieValue
??? ??? Cookie cookies[] = request.getCookies();
??????????????? String cookieValue = null;
??????????????? if(cookies!=null){
???????????????????? for(int i=0;i
??? ??? ??? if (cookieDomainName.equals(cookies[i].getName())) {
??? ??? ??? ??? cookieValue = cookies[i].getValue();
??? ??? ??? ??? break;
???????????????????????? }
???????????????????? }
??????????????? }
???? ??? //如果cookieValue为空,返回,
??? ??? if(cookieValue==null){
??? ??? ??? return;
??????????????? }
????????????? //如果cookieValue不为空,才执行下面的代码
????????????? //先得到的CookieValue进行Base64解码
????????????? String cookieValueAfterDecode = new String (Base64.decode(cookieValue),"utf-8");
????????????? //对解码后的值进行分拆,得到一个数组,如果数组长度不为3,就是非法登陆
????????????? String cookieValues[] = cookieValueAfterDecode.split(":");
????????????? if(cookieValues.length!=3){
???????????????????? response.setContentType("text/html;charset=utf-8");
???????????????????? PrintWriter out = response.getWriter();
???????????????????? out.println("你正在用非正常方式进入本站...");
???????????????????? out.close();
???????????????????? return;
????????????? }
????????????? //判断是否在有效期内,过期就删除Cookie
????????????? long validTimeInCookie = new Long(cookieValues[1]);
????????????? if(validTimeInCookie < System.currentTimeMillis()){
???????????????????? //删除Cookie
???????????????????? clearCookie(response);
???????????????????? response.setContentType("text/html;charset=utf-8");
???????????????????? PrintWriter out = response.getWriter();
???????????????????? out.println("");你的Cookie已经失效,请重新登陆
???????????????????? out.close();
???????????????????? return;
????????????? }
????????????? //取出cookie中的用户名,并到数据库中检查这个用户名,
????????????? String username = cookieValues[0];
????????????? //根据用户名到数据库中检查用户是否存在
????????????? UserDAO ud = DaoImplFactory.getInstance();
????????????? User user = ud.selectUserByUsername(username);
????????????? //如果user返回不为空,就取出密码,使用用户名+密码+有效时间+ webSiteKey进行MD5加密
????????????? if(user!=null){
???????????????????? String md5ValueInCookie = cookieValues[2];
???????????????????? String md5ValueFromUser =getMD5(user.getUserName() + ":" + user.getPassword() + ":" + validTimeInCookie + ":" + webKey);
???????????????????? //将结果与Cookie中的MD5码相比较,如果相同,写入Session,自动登陆成功,并继续用户请求
???????????????????? if(md5ValueFromUser.equals(md5ValueInCookie)){
??????????????????????????? HttpSession session = request.getSession(true);
??????????????????????????? session.setAttribute("user", user);
??????????????????????????? chain.doFilter(request, response);
???????????????????? }
????????????? }else{
?????? ??? ??? ???? //返回为空执行
???????????????????? response.setContentType("text/html;charset=utf-8");
???????????????????? PrintWriter out = response.getWriter();
???????????????????? out.println("cookie验证错误！");
???????????????????? out.close();
?????? ??? ??? ???? return;
??? ????? }
?????? }
?????? //用户注销时,清除Cookie,在需要时可随时调用------------------------
?????? public static void clearCookie( HttpServletResponse response){
????????????? Cookie cookie = new Cookie(cookieDomainName, null);
????????????? cookie.setMaxAge(0);
????????????? cookie.setPath("/");
????????????? response.addCookie(cookie);
?????? }
??? //获取Cookie组合字符串的MD5码的字符串----------------------------------------
??????? public static String getMD5(String value) {
?????????????? String result = null;
?????????????? try{
????????????????????? byte[] valueByte = value.getBytes();
????????????????????? MessageDigest md = MessageDigest.getInstance("MD5");
????????????????????? md.update(valueByte);
?????????????????????? result = toHex(md.digest());
?????????????? } catch (NoSuchAlgorithmException e){
????????????????????? e.printStackTrace();
??? ?????? }
?????????????? return result;
???????? }
??? //将传递进来的字节数组转换成十六进制的字符串形式并返回
??????? private static String toHex(byte[] buffer){
??? ??? StringBuffer sb = new StringBuffer(buffer.length * 2);
??? ??? for (int i = 0; i < buffer.length; i++){
??? ??? ??? sb.append(Character.forDigit((buffer[i] & 0xf0) >> 4, 16));
??? ??? ??? sb.append(Character.forDigit(buffer[i] & 0x0f, 16));
??????????????? }
??????????????? return sb.toString();
??????? }
}
下面的是对CookieUtil工具类各方法的调用演示：
User.java
封装用户信息的JavaBean对象模型
package com.itcast.bean;
public class User {
?????? private int id;
?????? private String userName;
?????? private String password;
?????? public String getPassword() {
????????????? return password;
?????? }
?????? public void setPassword(String password) {
????????????? this.password = password;
?????? }
?????? public String getUserName() {
????????????? return userName;
?????? }
?????? public void setUserName(String userName) {
????????????? this.userName = userName;
?????? }
?????? public int getId() {
????????????? return id;
?????? }
?????? public void setId(int id) {
????????????? this.id = id;
?????? }
}
-------------------------------------------------
AutoLogonFilter.java
过滤器程序,可在WEB-INF/web.xml中设置过滤规则,本文对过滤规则不作介绍，此程序主要作用是检查用户在上一次登陆时是否保存了Cookie，如果保存了，就处理Cookie信息，并帮助用户自动登陆
本程序主要调用了CookieUtil.java中的读取与自动登陆方法，即readCookieAndLogon方法
package cn.itcast.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import cn.itcast bean.User;
import cn.itcast.util.CookieUtil;
public class AutoLogonFilter implements Filter {
?????? public void destroy() {
?????? }
?????? //保存cookie时的cookieName,与CookieUtil.java中的设置相同
?????? private final static String cookieDomainName = “cn.itcast”;
?????? public void doFilter(ServletRequest req, ServletResponse resp,
???????????????????? FilterChain chain) throws IOException, ServletException {
????????????? HttpServletRequest request = (HttpServletRequest)req;
????????????? HttpServletResponse response = (HttpServletResponse)resp;
????????????? HttpSession session = request.getSession(true);
????????????? User user = (User)session.getAttribute("user");
????????????? //如果封装的user不为空,说明已经登陆,则继续执行用户的请求.下面的就不处理了
????????????? if(user!=null){
???????????????????? chain.doFilter(request,response);
???????????????????? return;
????????????? }
????????????? //user为空，说明用户还没有登陆,就尝试得到浏览器传送过来的Cookie
????????????? Cookie cookies[] = request.getCookies();
????????????? String cookieValue = null;
????????????? if(cookies!=null){
???????????????????? for(int i=0;i
??????????????????????????? if (cookieDomainName.equals(cookies[i].getName())) {
?????????????????????????????????? cookieValue = cookies[i].getValue();
?????????????????????????????????? break;
??????????????????????????? }
???????????????????? }
????????????? }
????????????? //如果cookieValue为空,也继续执行用户请求
????????????? if(cookieValue==null){
???????????????????? chain.doFilter(request,response);
???????????????????? return;
????????????? }
????????????? //cookieValue不为空执行下面的方法,调用CookieUtil.java中的readCookieAndLogon方法
????????????? try{
???????????????????? CookieUtil.readCookieAndLogon(cookieValue, request, response, chain);
????????????? }catch(Exception e){
???????????????????? e.printStackTrace();
????????????? }
?????? }
?????? public void init(FilterConfig arg0) throws ServletException {
?????? }
}
CheckLogonServlet.java
验证用户登陆信息的Servlet，此程序调用了CookieUtil.java中的saveCookie方法
package cn.itcast.servlet;
/*
?* update 2007.09.23 by lyhapple
?* 检查用户登陆
?* */
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import cn.itcast.bean.User;
import cn.itcast.dao.UserDAO;
import cn.itcast.factory.DaoImplFactory;
import cn.itcast.util.CookieUtil;
public class CheckLogonServlet extends HttpServlet {
?????? public void doGet(HttpServletRequest request, HttpServletResponse response)
???????????????????? throws ServletException, IOException {
????????????? doPost(request, response);
?????? }
?????? public void doPost(HttpServletRequest request, HttpServletResponse response)
???????????????????? throws ServletException, IOException {
????????????? request.setCharacterEncoding("utf-8");
????????????? String username = request.getParameter("username").trim();
????????????? String password = CookieUtil.getMD5(request.getParameter("password"));
????????????? String remeberMe = request.getParameter("remeberMe");
????????????? HttpSession session = request.getSession(false);
????????????? // 将接收到的用户名传递到UserDao的checkUser方法中,检查用户
????????????? // 返回一个User类型的对象
????????????? UserDAO ud = DaoImplFactory.getInstance();
????????????? User user = ud.selectUserByUsername(username);
????????????? if (user == null) {
???????????????????? request.setAttribute("checkUserError","");用户名不存在,请先注册
???????????????????? request.getRequestDispatcher("index.jsp").forward(request, response);
???????????????????? return;
????????????? }
????????????? if(!password.equals(user.getPassword())){
???????????????????? request.setAttribute("checkPasswordError","");密码输入错误,请重新输入
???????????????????? request.getRequestDispatcher("index.jsp").forward(request, response);
???????????????????? return;
????????????? }
????????????? //保存Cookie,这里调用了CookieUtil.java中的saveCookie方法，将上面的user对象作为参数传递
????????????? if ("on".equals(remeberMe)) {
???????????????????? CookieUtil.saveCookie(user, response);
????????????? }
????????????? //在Session中保存用户信息，并转向用户的个人信息页面
????????????? session.setAttribute("user", user);
????????????? request.getRequestDispatcher("User/userInfo.jsp").forward(request,response);
?????? }
}
UserDAO.java与DaoImplFactory.java属于持久层相关的程序，这里就不贴出来了，读者可根据自己需要选择不同的持久层框架，在本程序中只要实现查询用户的功能就可以了
(摘自:http://i18n.iteye.com/blog/130306)